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Overview On December 20, 2005, EPA proposed revisions to the National Ambient Air Quality Standards (NAAQS) for particle pollution. The proposed revisions address two categories of particle pollution: – fine particles (PM2.5), which are 2.5 micrometers in diameter and smaller; and – inhalable coarse particles (PM10-2.5), which are smaller than 10 micrometers in diameter but larger than PM2.5. Simultaneously, EPA proposed amendments to its national air quality monitoring requirements, including those for monitoring particle pollution. The proposed changes include the design of a network to monitor PM –

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PM2.5 – Primary 24-hour Standard Under the proposal, EPA would revise the level of the 24-hour standard from the current level of 65 μg/m3 to 35 μg/m3. EPA also is considering alternative levels for the 24-hour standard, between the range of 35 and 30 μg/m3 and is soliciting public comment on these levels. In addition, the Agency will take comment on alternative approaches for selecting the level of the standard, and on levels as high as the current level of 65 μg/m3 and as low as 25 μg/m3.

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PM2.5 – Primary Annual Standard EPA is proposing to retain the current annual standard at 15 μg/m3 EPA is considering and is seeking public comment on lower alternatives for the annual standard including 14 and 13 μg/m3. In addition, the Agency will take comment on alternative views including a standard as low as 12 μg/m3.

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PM2.5 – Secondary Standards The proposal would set the secondary standards for both the annual and 24-hour standards at levels identical to the primary standards EPA also is taking comment on whether to set a separate PM2.5 standard, designed to address visibility (principally in urban areas) – At levels within a range of 20 to 30 μg/m3, and – On averaging times within a range of four to eight daylight hours

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Inhalable Coarse PM – Moving from PM10 to PM EPA’s current standards for coarse particles (PM10) were set in These standards, a 24-hour standard of 150 μg/m3, and an annual standard of 50 μg/m3, apply to particles 10 micrometers in diameter and smaller. The proposed revisions would change the definition of standard so that it covers only particles between 10 and 2.5 micrometers in diameter also known as PM or “inhalable coarse particles.”

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PM Standards The proposed new PM standard would be a 24-hour standard, at 70 μg/m3. EPA is not proposing an annual standard for PM Under the proposal, the secondary 24-hour standard for PM would be identical to the primary standard.

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Inhalable Coarse PM – Moving from PM10 to PM EPA proposes to qualify coarse PM to include: – Any ambient mix of PM that is dominated by resuspended dust from high-density traffic on paved roads and PM generated by industrial sources and construction sources. – This definition excludes any ambient mix of PM that is dominated by rural windblown dust and soils and PM generated by agricultural and mining sources. – Agricultural sources, mining sources, and other similar sources of crustal material are not be subject to control in meeting this standard The indicator is not defined or limited to any specific geographic area, but includes a mix of PM in any location that is dominated by these sources.

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Revoking the Current PM10 Standard EPA is proposing to revoke the current 24-hour PM10 standard, except in urbanized areas that have both: 1) one or more violating PM10 monitors; and 2) a population of 100,000 or more. – This standard would remain in place in these areas until the Agency has completed attainment and nonattainment designations for PM – EPA is taking comment on whether the 24-hour PM10 standard should be retained in areas with a population less than 100,000 but where the majority of the ambient mix of PM is generated by high density traffic on paved roads, industrial sources, and construction sources. The Agency is proposing to immediately revoke the current annual PM10 standard in all areas.

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Potential Timeline if PM Standard is Finalized

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Advanced Notice of Proposed Rulemaking: Transition to New or Revised PM NAAQS February 9, 2006 Comments due April 10, 2006

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What issues are discussed in the ANPR? Proposed options for transitioning from 1997 PM2.5 NAAQS to any new 2006 PM2.5 NAAQS Timelines for implementation of any new 2006 PM2.5 NAAQS Timelines for implementation of any new PM NAAQS Transition from the PM10 standards to any new PM NAAQS What emission inventory requirements should apply to PM2.5 and PM NAAQS Next steps